The Douglas F3D Skyknight

v2.0.1 / 01 dec 13 / greg goebel / public domain

* The Douglas Skyknight was one of the first purpose-built jet night
fighters, which served with distinction in the Korean War and survived to put
in useful service in the Vietnam War as well. This document provides a
history and description of the Skyknight.

* In 1945, the US Navy began studies for a jet-powered carrier-based night
fighter, resulting in issue of a request specifying a two-seat aircraft with
long range radar and good performance. Douglas, Grumman, Curtiss, and
Fleetwings submitted proposals, with Douglas awarded a contract on 3 April
1946 for delivery of three prototypes with the designation "XF3D-1
Skyknight". Notice the spelling was "Sky-Knight", not "Sky-Night".

Development was conducted by a team under the well-known Ed Heinemann at the
Douglas division in El Segundo, California. The first prototype XF3D-1 made
its initial flight on 23 March 1948, with test pilot Russell Thaw at the
controls. All three prototypes were sent to Edwards Air Force Base in
October 1948 for service trials. The Air Force was interested in the
Skyknight for a time, since the Northrop F-89 Scorpion all-weather
interceptor was suffering from development problems, but the USAF decided to
acquire the Lockheed F-94 Starfire interceptor, a derivative of the Lockheed
T-33 trainer, as an interim solution until the Scorpion's bugs were ironed
out.

The Skyknight was of simple configuration, with:

Mid-mounted straight wings that folded vertically from the midsection.

A conventional tail arrangement.

Tricycle landing gear, with single wheels on all gear assemblies, the main
gear retracting outward into the wings, and the nose gear retracting
backwards.

A stinger-type arresting hook.

A skid with a tiny wheel on the end was mounted in front of the arresting
hook, and could be extended to protect the aircraft from bumping its tail on
takeoffs and landings. A hydraulically operated air brake was mounted on
each side of the fuselage behind the wings.

The Skyknight was powered by twin Westinghouse J34-WE-22 turbojets with 13.3
kN (1,360 kgp / 3,000 lbf) thrust each, fitted in nacelles mounted low on the
fuselage below the wings. The engines could be easily accessed for
maintenance, and dropping them out for replacement was a simple procedure.
However, it seems likely that the low position of the intakes made the
aircraft vulnerable to runway foreign object ingestion. The aircraft was
armed with four 20 millimeter cannon mounted in the underside of the nose,
with 200 rounds per gun. Internal fuel capacity was 5,116 liters (1,350 US
gallons). A 568 liter (150 US gallon) external tank or a 450 kilogram (1,000
pound) bomb could be carried under each wing.

The pilot and radar operator sat in a side-by-side configuration. The
ejection seats available at the time could not work safely with such a
seating arrangement, and an unusual escape mechanism was designed involving a
chute in the floor behind the flight crew. Pulling a lever would blow off
the rear half of the chute exit hatch in the belly between the engines, with
the front half serving as a windbreak. Each crew member would then pivot
around in his seat, grab a vaulting bar behind the seat, kick open a cockpit
exit door, and slide out the chute feet-first, one crew member at a time. It
wasn't a real ejection system, but it was better than nothing.

Westinghouse AN/APQ-35 radar system was fitted in the nose. The first two
prototypes had been fitted with the older SCR-720 radar since the AN/APQ-35
hadn't been available at the time. The AN/APQ-35 actually consisted of two
radars:

The AN/APS-21 search radar, which could locate fighter-size targets at a
range of 32 kilometers (20 miles).

The AN/APS-26 targeting radar, with a range of 3.2 kilometers (2 miles).

The AN/APS-21 could be used to locate a target, pass it over to the AN/APS-26
at close range for target tracking, and continue to scan for new targets. It
was one of the first "track while scan" radar systems ever developed.
Reliability was not the best, but that was true for all complicated avionics
systems of the era.

The prototype evaluation was successful, and led to an initial production
order for 28 "F3D-1" Skyknights in June 1948. The first production F3D-1
flew on 13 February 1950, and the type went into operational service with the
Navy VC-3 Squadron at Moffett Field, California, in December 1950.

* The F3D-1's airframe was similar to that of the XF3D-1, but it was fitted
with a stronger tail bumper wheel, and fully operational electronic systems
that increased the takeoff weight by over two tonnes. It also featured
uprated Westinghouse J34-WE-34 engines with 14.5 kN (1,475 kgp / 3,250 lbf)
thrust each, the new engines requiring larger nacelles. A few early
production F3D-1s were not fitted with the uprated powerplants due to engine
non-availability.

The F3D-1 was still definitely underpowered, and only the initial batch of 28
were produced. The F3D-1s remained stateside and were used for training
flight crew for the definitive Skyknight variant, the "F3D-2".

The F3D-2 was ordered in August 1949. The F3D-2 was originally planned to be
powered by twin Westinghouse J46-WE-3 turbojets with 20.5 kN (2,090 kgp /
4,600 lbf) thrust each. Unfortunately, development of the J46 proved
troublesome, and so the F3D-2 was completed with still further uprated
J34-WE-36/36A turbojets with 15.1 kN (1,540 kgp / 3,400 lbf) thrust each,
less powerful than the J46s, but still an improvement.

The first F3D-2 flew on 14 February 1951. The F3D-2's most visible external
difference from the F3D-1 was larger engine air intakes, provided to allow
greater airflow for the planned J46 turbojets. A spoiler system was added to
permit tighter turns and a higher roll rate, and an AN/APS-28 tail-warning
radar was also fitted. The AN/APS-28 was a relatively sophisticated sensor,
with a range of 6.5 kilometers (4 miles) and the ability to give range,
azimuth, and elevation information. Other improvements included a General
Electric G-3 autopilot, thicker windscreen armor glass, and more effective
air conditioning.

* A total of 237 F3D-2s was built, with the last produced in March 1952. The
Skyknight served with a number of US Navy and Marine squadrons, generally off
of land bases. It was nicknamed "Willie the Whale" for its less-than-sleek
appearance. Marine Squadron VMF(N)-513 was sent to Kunsan, Korea, with their
Skyknights in the spring of 1952, where the type served with distinction.

The USAF had operated Boeing B-29 Superfortress heavy bombers on daylight
raids over enemy territory early in the war, but suffered excessive losses to
North Korean MiG-15s, and so the bombers switched to night attacks, their
losses then declining considerably. However, by late 1951, the enemy had
refined their ability to direct MiG-15s against the Superfortresses using
ground radar control, and losses began to rise again. USAF F-94B Starfire
night fighters were put into service to protect the bombers, but for various
reasons they did not prove satisfactory in this role. Marine Skyknights were
pressed into service as night escorts instead and performed the mission very
well.

While the Skyknight was not as aerodynamically advanced as the sleek MiG-15
and did not have an excess of engine thrust by any means, its four cannon
packed a hefty punch, and it could easily out-turn a MiG-15 whose pilot was
foolish enough to get into a turning contest. Probably the biggest factor in
the Skyknight's favor was that the MiG-15 did not have search radar, being
directed to targets at night under ground radar control, and in a night fight
the MiG pilot was largely blind, while the Skyknight crew could "see"
perfectly well.

On the night of 2:3 November 1952, a Skyknight piloted by Marine Major
William Stratton, accompanied by radar operator Master Sergeant Hans
Hoagland, shot down what they reported from the exhaust pattern to be a
Yak-15 fighter, and claimed a confirmed kill since the Skyknight flew through
debris, narrowly evading damage. Russian records indicate the target was
actually a MiG-15 -- the Yak-15 was really not suited for operational use,
and wasn't used in combat in Korea or anywhere else -- and though the
Skyknight set the MiG on fire, the pilot managed to extinguish the flames and
get back to base. The MiG was fully operational in a few days, a tribute to
its rugged construction. However, five days later, on the night of 7:8
November, another Skyknight under the command of Marine Captain Oliver R.
Davis with radar operator Warrant Officer D.F. "Ding" Fessler shot down a
MiG-15. Russian sources do confirm this kill and that the pilot, a
Lieutenant Kovalyov, ejected safely.

On 10 December 1952, a Skyknight piloted by Marine Lieutenant Joseph Corvi
with radar operator Sergeant Dan George spotted a "bogey" on radar. They
could not establish visual contact, but since no "friendlies" were supposed
to be in the area, they fired on the target. A kill was confirmed when
Sergeant George spotted a wing tumbling past them. It turned out to be one
of the little Po-2 biplanes used by the North Koreans to harass UN forces at
night. The Po-2 was a difficult target, since it flew low and slow, it was
small and agile, and its mostly wooden construction did not show up well on
radar.

The Marine Skyknights claimed a total of at least six kills and no B-29s
under their escort were lost to enemy fighters. Two Skyknights were lost in
action for unknown causes.

* An F3D-3 with swept wings and J46 engines was planned, with a contract
placed for a large number of aircraft. Unfortunately, the delays in the J46
program meant that the J34 engine would have to be used, and studies
demonstrated that with J34 engines the F3D-3 would show little performance
improvement over the F3D-2. The order was canceled in early 1952. There
was no further new production of Skyknights.

The Skyknight was clearly a first-generation jet fighter, and as such was
quickly pulled out of first-line service after the Korean War, to be replaced
by more sophisticated aircraft such as the Douglas F4D Skyray. However, the
type was updated and converted to special uses:

In 1952, some F3D-2s were given a "special armament" fit -- details are
unclear -- and given the new designation "F3D-2B".

One of the three XF3D-1 prototypes was modified in late 1952 as a test
aircraft for the new Sparrow I air-to-air missile (AAM), and at least
twelve F3D-1s were also modified with four stores pylons under the wings
to carry the Sparrow I for development testing. These F3D-1s were given
the new designation "F3D-1M".

16 F3D-2s were similarly modified and redesignated "F3D-2M". Apparently
the cannon were removed in Sparrow-armed Skyknights, and the aircraft were
fitted with more powerful radar in a longer nose as well.

The Skyknight was also updated to trainer configurations, including five
"F3D-2T" night fighter trainers and 55 "F3D-2T2" radar trainers.

From 1956, the US Marines converted a number of Skyknights to an
electronic countermeasures (ECM) and electronic intelligence (ELINT)
configuration, with this variant redesignated "F3D-2Q". The radar was
removed from the nose and replaced with the appropriate "black boxes", and
it appears that chaff dispensers were carried as well. Some sources claim
the cannon armament was removed, but some aircrew reports suggest this was
not always done.

According to other reports by aircrew, the Skyknight was very well suited for
use as a trials or countermeasures platform, since it had a large equipment
bay in the fuselage, accessed through a door in the belly and big enough to
allow a technician to stand up.

* In 1962, the US military consolidated their aircraft designation schemes,
and Skyknight variants still in operation were redesignated as follows:

In 1965, the US began to ramp up the air war against North Vietnam, and the
US military found itself short of countermeasures aircraft to protect strike
packages. The EF-10B was one of the few assets on hand, and in April 1965 a
handful of them were sent to Da Nang airbase in South Vietnam to support both
US Navy and US Air Force raids over North Vietnam.

There were never more than about ten EF-10Bs available, and they were sent on
numerous "Fogbound" missions, pinning down the locations of enemy radar
stations and passing off their coordinates for attack by defense-suppression
aircraft, or blinding the radars with chaff and electronic jammers. Despite
their age, the EF-10Bs were very effective, and they were heavily tasked well
into 1966. By late 1966, Douglas RB-66 Destroyers were taking over the
countermeasures role for the Air Force, with the EKA-3B Skywarrior and later
the EA-6A Prowler taking over countermeasures for the Navy. However, some
EF-10Bs were upgraded with new avionics in 1967, being known as "Super
Whales". The Marine EF-10Bs continued to fly in Vietnam until 1969; the type
was finally removed from operational service in 1970.

A number of TF-10Bs were used as test and trials platforms into the early
1980s. These aircraft were the victims of bizarre Frankenstein
modifications, with noses of other aircraft such as the Skyhawk grafted on to
perform tests of radar systems. No Skyknights are now in flying condition,
though a number are in static display in museums and US military bases.

* In the late 1950s, Douglas worked on a follow-on of sorts to the SkyKnight,
the "F6D Missileer". It grew out of US Navy worries in the later 1950s about
fleet air defense, aggravated by the Soviet development of antiship missiles
that could be used to attack a carrier group; defense against such high-speed
missiles was clearly problematic.

One part of the solution to the problem was a carrier-based radar airborne
early warning (AEW) aircraft. That wasn't a new concept, the Navy having
operated such from just after the end of World War II, beginning with the
Grumman TBM-3W -- a serious modification of the Avenger torpedo bomber -- and
culminating in the 1960s with the Grumman E-2 Hawkeye. However, an AEW
aircraft could only give warning; the AEW aircraft had to be linked to some
sort of weapons platform that would destroy the threats.

In 1957, the US Navy began work on what was known as a "fleet defense
fighter". It wasn't to be a fighter in the traditional sense of the word; it
was essentially a flying AAM carrier, with long-range AAM armament, powerful
radar, and long endurance. It didn't need to be dogfighter, and so the Navy
specified subsonic performance -- a backwards-seeming step in an era when
Mach 2 performance was regarded as all but mandatory for a combat aircraft.

The fleet defense fighter was a "weapons system", necessarily involving three
development programs: one for the AAMs, one for the radar, and one for the
aircraft itself:

In late 1958, Bendix was awarded the contract to develop the "AAM-N-10
Eagle" AAM, a technological marvel for the time, with a range of 185
kilometers (115 miles), a top speed of Mach 4.5, and active radar homing.
It was huge for an AAM, a two-stage missile with a length of 4.9 meters
(16 feet) and a weight of 584 kilograms (1,288 pounds), including a 50
kilogram (110 pound) warhead. The Eagle had a "home on jam" mode that
could be used to extend its range beyond radar limits.

At the same time, Westinghouse was awarded the contract to develop the
long-range "AN/APQ-81" radar. It had a maximum range against bomber-sized
targets of up to 220 kilometers (135 miles), with the ability to track
eight targets simultaneously and provide midcourse guidance corrections to
the Eagle missiles. Work on the Hawkeye AEW aircraft was initiated in
parallel.

Vought, Douglas, Grumman, McDonnell, and North American all submitted
designs for the aircraft itself, with Douglas winning the contract for the
"F6D Missileer" in July 1960. Two prototypes were planned.

The F6D had a configurational resemblance to the Skyknight, featuring a
side-by-side cockpit for pilot and radar operator, twin podded engines, and
straight flight surfaces. The wings were mounted high instead of at
mid-fuselage, though they still folded up at mid-span. Three Eagle AAMs
could be carried on pylons under each wing, plus two on the belly, for a
total of eight missiles. The Missileer was to be powered by a
non-afterburning version of the new Pratt & Whitney TF30 bypass turbojet.
The F6D would have tricycle landing gear, all gear assemblies with twin
wheels, the main gear tucking into the fuselage, and a stinger-type arresting
hook. Presumably the Missileer had ejection seats; it is unclear if the
radar operator had secondary flight controls, which would have come in handy
to spell the pilot every now and then.

Some sources claim that there were doubts from the outset about the F6D since
it was clearly not an air-superiority fighter as such -- but that was stated
in the specification, it was only intended to be a long-range air-defense
platform. In principle, dogfighting wasn't a concern because the Eagle
missile would destroy any intruder before they knew what hit them; the
expected adversaries were Soviet missile carrier aircraft and antiship
missiles, the missiles possibly launched from Soviet warships or submarines,
meaning dogfighting was irrelevant anyway. If dogfighting was required, the
Navy was acquiring other assets, such as the Vought F8U Crusader, for that
job.

However, the Missileer program was obviously going to be costly, and so the
outgoing Eisenhower Administration was unenthusiastic about pushing it,
preferring to leave the decision to invest in the program to the next
presidency. When the Kennedy Administration took office in early 1961, the
new defense secretary, Robert McNamara, was big on "commonality" between the
US armed services; he felt that the Navy's fleet defense fighter could be
developed as a variant of the Air Force's General Dynamics F-111 strike
fighter, with the Navy variant designated the "F-111B". Of course, the
Missileer was cancelled without ever being flown.

The F-111B would turn out to be a fiasco and would never serve with the US
Navy; when the F-111B program collapsed, Grumman -- which had been developing
the F-111B as a subcontractor to General Dynamics -- offered an alternative
design for a fleet defense fighter. It would emerge as the "F-14 Tomcat",
armed with the Hughes AIM-54 Phoenix long-range AAM, the name of "Phoenix"
apparently hinting at a resurrection of the "Eagle", guided by Hughes
AN/AWG-9 radar, originally developed for the F-111B. However, that is
another story.

It is difficult in hindsight to know if the F6D was a good idea or not.
Certainly, nobody would have ever considered it a fighter, but a
carrier-based "flying truck" would have had a range of applications of its
own, such as tanker or EW platform -- a flexibility eventually demonstrated
by an operational "flying truck", the Lockheed S-3 Viking. The Missileer
having never come close to flying, speculation is all we have left.

* Despite the fact that most sources speak well of the Skyknight, one US
Marine familiar with the aircraft from his Vietnam days said on an Internet
bulletin board that it was known as the "Drut", a term whose meaning can be
deciphered by reading it backwards. Some claim that this unflattering
nickname was obtained from the escape system, with the crew "flushed out" of
the cockpit backwards through the escape chute. However, the age of the
Skyknight by the Vietnam era might have had something to do with it as well.

* All my aviation documents are written from secondary sources, and while
this is adequate to give a fairly clear description of an aircraft, there's
generally a few contradictions and fuzzy points. In the case of the
Skyknight, descriptions of the AN/APQ-35 radar system are confusing and
contrary, particularly since it actually consisted of two separate radars,
the AN/APS-21 and AN/APS-26, working in conjunction, and only one document
actually made a specific connection between them all. Range figures also
vary widely from source to source; as it turns out, radar range has to be
specified relative to the size of a target, and not surprisingly a radar can
pick up a heavy bomber from much farther away than it can pick up a fighter.
I use conservative range specifications in this document.

* Sources include:

THE ILLUSTRATED ENCYCLOPEDIA OF 20TH CENTURY WEAPONS AND WARFARE, edited
by Bernard Fitzsimons, 1978 edition.

THE ILLUSTRATED HISTORY OF FIGHTERS, edited by Bill Gunston, Exeter Books,
1981.

VIETNAM: THE WAR IN THE AIR by Rene J. Francillon, Arch Cape Press, 1987.

"Fighter Combat Over Korea", WINGS OF FAME, Volume 3/4, 1996, 112.

"F3D Skyknight: A Match For The MiG" by Warren E. Thompson, COMBAT
AIRCRAFT, December 2000, 72:75.

A very thorough website document on the Skyknight by aviation enthusiast Joe
Baugher was also consulted for additional details.